During immunoassay that uses a flow cell, automated analyzers, in particular, that employ magnetic particles quantitatively analyze constituents of a substance to be measured, by causing antigen-antibody reactions in a liquid mixture of a sample, magnetic particles, an antibody that binds the magnetic particles to a substance in the sample that is to be measured, and a labeled antibody including a labeled substance.
To ensure that constituents not to be measured are removed from the liquid mixture (hereinafter, referred to as the reaction solution) that contains the constituents to be measured, the magnetic particles, and the labeled substance, a magnetic separator such as a magnet is provided on a flow channel through which the reaction solution flows.
Because of their binding to the magnetic particles, the constituents to be measured are captured by the magnetic separator, but the constituents not to be measured flow intact without being captured. The constituents to be measured can therefore be separated from those which are not to be measured.
When a voltage is applied to the thus-separated constituents to be measured, the labeled substance that has bound to each of these constituents will emit light, so the quantity of constituents to be measured can be determined by measuring the amount of light emitted. Such an analyzer is described in Patent Document 1, for example.